Tool holding devices



TOOL HOLDING DEVICES Filed Dec. 1.1953

United States Patent TOOL HOLDING DEVICES Alois Kaltenbach, Biberach-Riss, Germany Application December 1, 1953, Serial No. 395,549 Claims priority, application Germany December 2, 1952 6 Claims. (Cl. 279-79) This invention relates to tool holding devices, and more particularly to devices having an angle-piece head for tools, such as are used for dentistry purposes, having a conical stem portion or shank, which tools are secured against axial displacement by locking means engaging in an annular groove of the stem.

Angle-piece heads for tools comprising a conical stem are already known in which the tool stem is secured against axial displacement by the fact that a disc provided with a recess and movable perpendicular to the tool stem engages in an annular groove of the latter. The locking disc is secured against displacement perpendicular to the tool stem, in the position in which the tool stem is to be secured, by means of a sleeve adapted to be pushed thereon.

With these arrangements, it is not possible, during operation, reliably to avoid displacement of the securing sleeve and thus release of the tool. Furthermore, it is not easy to' change the tools with the known arrangement.

Angle-piece heads for dentistry purposes are also known in which the locking means are actuated by a springloaded bush which is arranged axially of the stem and projects from the rear head end of the angle-piece. This means serves for locking a drill with a cylindrical stern and rotates with the latter in order in this manner to obviate the wear to which a stationary retaining spring, hitherto employed for the same purpose and engaging in the annular groove of the drill stem, was subjected.

Whereas the locking members in this latter known construction are not loaded in any way by the spring arranged inside the actuating bush, the conical end of the tool stem according to the invention is axially loaded by the spring through the locking member in the sense of a pressing action on a corresponding opposing cone surface of the drive for the drill sleeve. For this purpose, the spring loaded bush comprises a bar extending beyond the conical part of the tool stem and resilient in the direction towards the axis of rotation, the rear end of said bar engaging in the manner of a locking projection or pawl in the annular groove of the stem. In this manner, while at the same time reducing the number of separate parts of which the angle-piece head is composed, there is obtained a locking and tensioning means for the tool equipped with a conical stem.

One constructional example of the arrangement according to the invention is shown in the drawings where- 1n:

Figure l is an elevational view of an angle-piece head,

Figure 2 is a longitudinal section of the angle-piece head to a larger scale,

Figure 3 is a section on the line 3-3 of Figure 2, and

Figure 4 is a section on the line 4-4 of Figure 2.

The arrangement illustrated in the drawings, comprises a tool stem indicated at 1, the latter having a rearwardly extending conical section 2 which is mounted ice in an inner bush 3 ofdrive means for the drill holder.

The said drive means also includes an outer sleeve orholder 3a, which is connected to the holder 3 by soldering, welding or the like. The outer sleeve 3a carries a driving sprocket 3b of the drill holder'drive.

The drive means is mounted in the head 4 of the drill holder and is supported at the forward end by a bushing 5 screwed into the head 4, and at the rear end by a bushing 6 fitted into the head. The tool stem is held in position by locking means comprising a resilient bar 7 which is arranged in a longitudinal groove 8 of the bush 3 of the drill holder drive. The resilient bar 7 is formed at its forward end 9 with a locking projection or pawl 10 which engages in an annular groove 11 of the tool stern in the locking position. The locking pawl 10 has a bevelled portion 12 so that the part 9 of the locking device does not strike against the cylindrical tool stem 1 during operation of the locking means. The part 9 of the locking means bears on the wall of the sleeve 3a at 13 in the locking position. The resilient bar 7 is rigidly connected at its rear end to a bush 14. The bush 14 is closed at its rear end by a wall 15 and the rear end portion of the bush normally projects from the angle-piece head. Arranged inside the bush 14 is a compression spring 16 and the bush 14 is guided in a part 17 screwed into the sleeve 3a.

The locking means is operated by pressing on the Wall 15 of the bush 14 so that the resilient bar 7 bears with its forward end 9 on the wall 18 of the bushing 5. The tool stem can then be introduced into or withdrawn from the angle-piece head.

After insertion of the tool stem, the locking means is allowed to slide of its own accord into the locking position. This is effected by releasing the pressure applied to the compression spring 16 arranged in the bushing 14. In order to ensure that the forward end 9 of the resilient locking bar 7 does not bind during the return movement, the outer sleeve 3a of the drive member for the drill holder is bevelled as at 19 and the forward part 9 of the pawl or locking member is bevelled as at 20. A pin 21 is fixed in the bush 3 of the drive member of the drill holder in order to prevent the tool stem 2 turning in relation to the said drive member.

I claim:

1. A device for holding tools having a conical stem, said device comprising an angle-piece head, a rotatable drive member in said head, means in said drive member for holding a conical tool stem and including a conical recess complementary to the stem, and means for releasably locking a tool stem in said drive member, said locking means including a spring-loaded bush displace ably mounted in said head and normally projecting from one end thereof, a locking part carried by said bush and operable to apply wial loading to a conical tool stem for engagement with the conical recess, and means on said drive member engageable by said part for releasably holding said part in locking engagement with the tool stem.

2. In combination, a tool having a stem including a conical shank and a groove located forwardly of the shank, and a device for holding the tool comprising an angle-piece head, a rotatable drive member in said head for engaging the conical shank and means for releasably locking the tool stem in said drive member including a spring-loaded bush displaceably mounted in said head and normally projecting from one end thereof, a resilient bar connected to said bush and movable towards and away from the axis of rotation of said drive member, and a locking projection at the free end of said bar engageable in said groove.

3. A device as claimed in claim 2, wherein said pro nd r l i t rq si a d a dj n imdi a groove. 7, V

5, A deviceas elain ied in clainri A, wlierein .ibe forward end of theresilient bareornprisingihe locking-projection is he1 d ..in the=lockingposition zby a'wallrsectionl of the drive member. 7

6. A device as claimed in claim 5 wherein .the drive member ismounted at the front and rearends'by bushings fitted in the head.

References Cited in the fire of this patent UNITED "STATES PATENTS Hesse Feb. 6, 1894 Clouse Dec. 21, 1909 Brown Dec. 22, 1931 Beardsley Apr. 2, 1940 Brinson Mar. 19, 1946 Petre May 13, 1952 FOREIGN PATENTS 7 z 7 Germany Aug. 1, 1935 Germany Oct. 19, 1937 France Dec. 17,1-11943 

